This invention relates to electronically-conductive polymers, and to composite articles or polymer blends containing such polymers. More specifically, this invention relates to electronically-conductive polymers having both improved conductivity and processability, and to composite articles comprising these.
Intrinsically conductive polymer compositions (ICPs), such as conductive forms of polyaniline, which are relatively thermally stable may be used to produce a thermally stable processible composition containing the ICP and one or more thermoplastic, solution-processible or thermoset polymers. See e.g., U.S. Pat. No. 5,160,457. U.S. Pat. No. 5,232,631 describes a composition comprising polyaniline, a solvent or plasticizing liquid, and a protonic acid solute which has been functionalized so that the polyaniline:protonic acid combination is compatible with nonpolar or weakly-polar organic liquids or solutions, or molten or liquefied oligomers, polymers or polymer mixtures. However, while the combination of the doped polyanilines and polymers described in these patents are thermally and solution processible to some extent, a relatively high weight content of the doped polyaniline is required to achieve the required conductivity for certain applications, such as electrostatic painting applications. The physical properties of the blends may also be less than desirable for certain applications. For example, the high acid dopant content of such compositions is relatively corrosive to metal and is a safety hazard. Corrosivity is particularly detrimental in applications, wherein the electronically-conducting polymer composite is processed through metal equipment, or the composite contacts metal during use. EP Application 582,919 describes a method for lowering the polyaniline content of such a blend by adding a metal salt to the blend. However, the physical properties of such a blend, particularly its impact resistance at low temperatures, may be less than desirable for certain applications.
Complexes of polyaniline and dopants having a relatively high molecular weight are also known and described, for example, in U.S. Pat. No. 5,378,402. Such complexes have relatively high solubility in solvents and matrix polymers, but their conductivity may be less than desirable for certain applications. Conductive polymers doped with more than one dopant are known and are described, for example, in U.S. Pat. No. 5,378,404. Such polymers are prepared by partially un-doping an ICP solid particle doped with a first dopant, and then doping with the second dopant which is more compatible with a matrix polymer with which the conductive polymer is to be blended. However, the thermal stability and processing characteristics of the doped polymer may still be less than desirable.